The Influence of Molecular Weight on the Properties of Meta‐Aramid: Thermal Stability, Crystallinity, and Mechanical Properties

ABSTRACT Meta‐aramid is expected to become basic materials for creating new quality productive forces due to its excellent thermal stability and physical strength. In this study, a series of PMIA with different intrinsic viscosities were prepared to investigate the effect of molecular weight on various properties of PMIA. By using the same dry–wet process to prepare films, the influence of the processing on experimental results was eliminated. The prepared PMIA films were dense and uniform and exhibited self‐extinguishing ability after ignition. As the molecular weight increases, the thermal stability of PMIA is improved gradually. When the molecular weight increased to a certain extent, its thermal stability tended to stabilize. Under this film preparation process, molecular weight has almost no effect on the glass transition temperature and crystallinity of the material. In addition, the tensile strength and elongation at break showed a trend of first increasing and then decreasing with the increase of molecular weight, while the elastic modulus continued to decrease. Through molecular dynamics simulations, it was confirmed that the intermolecular interactions increased with the increase of molecular weight, and the effective entanglement of long molecular chains is also the main reason for the excellent performance of PMIA with high molecular weight.